Document EP 0 895 712 B1 discloses a lopper used to perform lopping, pruning and similar operations includes a lopping head provided with a spring-biased blade cooperating with a jaw, a drive mechanism, and an elongate housing. The drive mechanism includes first and second wheels rotatable relative thereto about a first axis. A head line couples the first wheel to the blade at a connecting point, and the second wheel is coupled to a driving line. The first wheel is eccentric relative to the second wheel so that a distance separating a region of a guiding surface of the first wheel from the first axis is smallest at a predetermined point of blade travel across the bight. The lopper also includes an intermediate handle and a lower handle selectively operable to actuate the blade relative to the jaw.
A problem with the lopper of the document is that the pull stroke of the handles is always the same length. A thin twig requires the same length of stroke as a thick branch, and therefore an excess work is needed when a lot of thin twigs need to be cut. If the mechanical advantage of the drive mechanism was made smaller for providing a shorter length of stroke, more force would be needed for cutting the branch.